Photographic brightness correction mask



Dec. 12, 1950 soE ETAL 2,533,452

PHOTOGRAPHIC BRIGHTNESS CORRECTION MASK Filed June 18, 1947 FIG l DENSITY L l ig E-q a GREEN EYPOSURE, mum DEVELOPMENT RED EXPOSURE, CYAN DEVELOPMENT PANCHROMAWC EMULSION LAYLR 5 I L I I r 4 T 42 l REMOVAL OF .S/LVEk FIG. 3.

B M c Y R a N FI G 4 C6 CB PAUL K. GLASOE DAVID DEAN l N V EN TORS ATTORNEYS processes. I 'cul'tand it would be more convenient if it could Patented Dec. 12, 1950 PHOTOGRAPHI-C BRIGHTNESS con- RECTION MASK Paul K. Giasoe and David Dean, Rochester, N. Y.,

assignors to Eastman Kodak Company, Rochester, Y., a corporation of New Jersey Application June 18, 1947, Serial No. 755,518

7 Claims.

This invention relatesto photography and more particularly to processes in color photography adapted to producing brightness. correction masks of use imprinting colored pictures.

In color processes of the type described in Mannes and Godowsky U. S. Patent 2,252,718 granted August 19, 1941., multi-layer color films are described which yield subtractively colored images by means of development with a primary takes place in. the black-and-white developer.

That is, it isv believed that development in a given layer exhausts the developer and releases halogen which slows down development in adjacent layers. The result of these effects, which will hereinafter be called interlayer eliects, is manifest in color pictures produced in processes such as mentioned, as images having varying degrees of brightness, for example,v red and magenta images may appear somewhat brighter than other colors in an original color film and when such a film is duplicated in" a similar color process the brightness differences are accentuated to the point of being objectionable.

In the corrective processes described in Hanson U. S. Patent 2,294,981 granted September 9', 1942; and Evans U. S. Patent 2,376,132 granted May 15, 1945. are provided colorless silverand colored photographic masks, respectively; which give general corrections for brightness differences in colored images resulting from incorrect absorptions of subtractive dye images. In these processes the use of these types of masks in conjunction with the film to be printed lowers the contrast ofthe image being printed and requires adjustment of the gamma of the duplicating This adjustment is often very diffibe' dispensed with. Furthermore, the processes do not provide means for selectively altering the brightnesses of individual colors.

One object of the present invention is to provide means of compensating for said photographic interl'ayer effects, which results in the rendering of colored images of more uniform brightness in multi-layer color films. Another object of the invention is to provide a masking 'method' which selectively corrects for brightness differences of colored images and particularly ofuse in duplicating processes. A further object of the invention is to provide a selective masking method which. does not appreciably alter the balance or a neutral scale in du licatin processes. Other objects will become evident in the following description of the invention.

These objects are accomplished by providing masks which selectively place density back of colors which are too bright when used in con-,- junction with a color him or transparency in a duplicating process.

The invention may be more readily understood by consideration of the accompanying drawings, wherein,

Fig. 1 shows the conditions which exist in one aspect of the invention in which a subtractively colored film, produced as described in. the above patents or by other means yielding subtracting images, in which the interlayer efiects have resulted in the cyan scale having a lower gamma in the neutral exposure scale area than in the red and magenta exposure scale areas with the net result shown of obtaining red and magenta colors which are brighter than. green and blue colors.

Fig. 2 shows in cross-sectional view, an inter:

mediate stage in forming one of the masks of the invention wherein both silver and dye images arecontained in the mask.

Fig. 3- is a cross-sectional view of a corrective mask, made in the manner of the invention; in printing relation to the photographic element? of Fig. 1 of which it is aphotographicrecord and whichmay be used in reproduction. processes. to correct for variations in brightness of individual colored images.

Fig. 4 shows in cross-sectional view the princi pal regions of light absorption of the color film of Fig. 1.

In the. drawings, Fig. 1. shows the cross-sectional appearance of a reversal processed original color film to be duplicatedin the manner of the invention, wherein, layers i, 2 and .i contain, respectively, yellow, magenta and. cyan dye images in areas of the film corresponding to various exposure scales of the. colors indicated across the top of the color film.

By exposure scale area or region is meant that'colored or neutral image-bearing area of a color film which has resulted directly or indirectly from exposure to a range of light intensities of one or more of the primary regions of the visible spectrum. For instance, the red exposure'scale region is that region of the film of Fig. 1 under R, in which are recorded the range of red light intensities from an. original red subject. Similarly, under N in Fig. l is shown the record of a range of intensities of white light from an original black-and-white subject. I

In Fig; 1, the gamma of cyan in the neutral exposure scale area is shown as being less than the gamma of the cyan in the red and magenta exposure scale regions. This constitutes one aspect 'ofthe invention which may be cured by a mask to be subsequently described. The result of the association of these unequal gamma's in the film is to make the reds and magentas appear brighter than the other images of the film because at the same Log. E values, points a in Fig. 1, the cyan in the scales of layer 3 has difierent densities shown as density levels N0, M and Re. A. further result of this condition is evident when the film is duplicated in a similar process. Asssuming that the gamma of the cyan in the neutral was 1.0 and the gamma in a red or magenta was 1.2; when the film is duplicated in a process of gamma 1.2 the gamma of the neutral becomes 1.0 but that of the cyan in the red or magenta scales becomes 1.44, thus the condition is accen tuated.

In the manner of the invention a panchromatic emulsion layer on a permanent or temporary support is preferably laminated base down onto the color film of Fig. l. A filtered exposure is made through the color film of Fig. 1 onto the emulsion layer with green light, for example. of wave lengths transmitted by a filter having the characteristics described on page 53 Fig. No. 61 of the publication Wratten Light Fi ters, seventeenth edition, 1945. This exposure in the upper stratum of the film is developed in an ordinary black-and-white developer of the following composition and washed:

Grams/lit r NazSOz 60 Hydroquinone 10 p-Methylamino-phenol sulfate 2 NazCOz 25 KBr 5 NaOH 5 NaCNS 5 Water to make 1 liter.

With the masking fi m in the same printing relation to the color film, a second exposure is made through the color fi m and the silver image in the masking film with red light such as transmitted by a filter of characteristics described on p. 37 Fig. No. 25 of the above publication. The masking film is then developed in a cyan color developer of the following composition:

Grams/liter Na2SO3 5 2-amine-5-diethyl amino toluene 2.8 NazCOs 15 KB! 5 p-Methylamino-phenol sulfate 0.9 NaCNS 1 NaOI-I 1.2 Cyan coupler 1.1 6-nitro benimidazole .05

Water to make 1 liter.

which may contain one of t e cvan couplers disclosed in Vittum U, S. Patent 2,362,598 ranted November 14, 1944. As shown in Fig. 2, the film now has silver images and dye ima es in the strata, but only dye ima es in areas corresponding to exposures through the magenta and red scales of the fi m of Fig. 1.

In Fig. 2 of the drawings the photographic element is shown as having a transparent support 4 carrying a panchromatic emulsion layer 5, which for the purposes of de crib ng the invention is divided horizontally into two strata one of which received the first exposure of the invention and in which was developed the sil er image; the other part receives the second ex osure and contains the subsequently deveoped dye image. The emulsion layer 5 is further divided vertically into segments corresponding to the regions of exposure through the exposure scales of the film of Fig. 1.

The printing relation shown in the drawings is that used when the two films are laminated emulsion to base.

The film is then bleached in a ferricyanidebromide bath and fixed in a hypo solution by conventional means. The result is to obtain a masking film as shown in Fig. 3 wherein the completely processed emulsion layer 3 contains only the cyan masking images I in printing relation to the magenta and red exposure scales of the orignal of Fig. 1. Therefore, it is apparent that when the films of Figs. 1 and 2 are used in registered printing relation when making a reproduction, the images I will lower the contrast of the magenta and red exposure scales but have no effect upon the gamma of the neutral scale and the resultant images will be of uniform brightness.

It is apparent that this and the following aspects of the invention may be applied not only to the correction of originals and reproductions produced in the manner of U. S. Patent No. 2,252,718 above identified, but is applicable to any subtractively colored film material requiring these corrections. Also, in forming the final colored images of the invention methods other than color-development, such as toning, may be used for suitably coloring the masking image.

According to a variation of the invention, it is occasionally desirable to place density back of colors other than the reds and magentas. For example, because of faulty exposure, processing, or peculiarities of an original film of the type shown in Fig. 1, it may be required to selectively place yellow back of blue images or magenta behind greens. The condition which exists in such a colored original is similar to that shown in Fig. '1 but when yellow is required back of blues, the

gamma of the. yellow scale in the blue and cyan exposure scales is higher than that of yellow in the neutral scale. When magenta is required back of the green and yellow exposure scales, the gamma of the magenta in these scales is greater than it is in the neutral exposure scale, Placing yellow back of blue and cyan; and magenta back of green and yellow is accomplished by using suitable wave len th of light for the two exposures and processing to th desired colors. To place yellow density back of blue and cyan, the first exposure is made to red light and after silver development t e second exposure is to blue light. Following develo ment in the color developer similar to that shown above but containing a yellow coupler, the silver im es are removed.

Sim larly to lace magenta back of greens the first ex osure is to b ue light and the second to green light. Processing is as previously described usin a m genta coupler in the color developer. Suitable ye low and magenta cou lers are those such as di closed in Seymour U. S. Patent 1,969,479 grant d Augu t 1934 and Mannes and Godowsky U. S. Patent 2,108,602 granted February 15, 1938. In most rocesses utilizing color films of the type de cribed by U. S. Patent 2252,718 abovementioned. the density of magenta in a pure red, represented by point r on the Log. E axis of the R exposure scale, Fig. 1, is less than it is in the maximum densit of the neutral scale, i. e., the magenta dye in the high exposure region of the red exposure scale has a lower density than in the unexpo ed reg on of the red exposure scale. Since the amount of mag nta in a red is a function of the amount of cyan in a red, as the cyan density in the red decreases, the amount of magenta also decreases; Toacorrectthis-deficiency of magenta, iti's necessary in. making: a reproduction to add magenta. as" anegatifve: function. of the cyan in the red and. magenta. exposure: scales only. This is accomplished". by" making.- the. first exposure as before to green light followed by; silver development and after red light. exposure through the color film and the silver image, processingv in a color developercontaining: a. magenta coupler; L or since most processes of this. type also require correction: for the excessivebrightness: of the red and magenta. colors, the developer may contain both cyan and magentaxconplers, in; suitable proportion or; if'd'esired; arblue-forming coupler such asalbha-naphthol canbe used together with the phenylene diamine developing agent.

In another aspect of the: invention, which conditionmay be present ima'ddition to-the previously mentioned conditions in a. color film;,the density of cyan in a green image of a subtractive film may be lower than the. density of yellow- (-see Fig. 1 under G in bottom layer). This may be caused by the overlapping green sensitivity of the red sensitive layer in. a. multi-layer' film of the type described above. Thus, when the green exposure of the original exceeds the-threshold value of the red sensitivelayer cyan. is removed in proportion to the' magent'a dye formed. The correction required calls for-a: negative cyan image back of only the green exposure scaleof the original being printed. In the manner of. the invention this is accomplished by using for the sensitive masking emulsion layer, a panchromatic material of the type described and; making the first exposure with magenta (red: and blue) light. and the second exposure through the. color film: and silver images with green light. Developmentbetween exposures". is carried: out as before in a bla'cli-and-white developer and after the second exposure with. acyan. coupler and none or only aminor proportion of magenta. coupler in the developer; After removing silver-images the recult is to place a. cyan image-- in the mask which, Wh'emirr printing: relation to" the original, places cyan density back ofv onll reen.

In Fig. 4: areshown, in cross-sectional View, the absorption gammas of the. dye images in the film of Fig. l. The areas under. the various-curves in the: yellow, magenta and cyanimage-bearing layers ill, Isl,.andlLrespectively, represent the light absorptions ot the various images composing the exposure scales indicated across the top of. the film. Thus. the area between. curves YB and YG is the blue absorption and thearea under YG the green. absorption of. the yellow dye in the corresponding area ofthe film of Fig. L. The areas under the minor absorption curves are colored complementary to. the indicated absorption gammas to show that the impure or minor absorptionsare efiectively equivalentto the presence in minor quantity of another colored. material.

The masks made as previouslydescribed may be used. in combination with a silver brightness correction mask. made as described in Hanson U. S. Patent 2,294,981, above, to correct for the impure absorptions of dyesas well as the relative brightness errors of color films. The colored masks of the invention may be combined with a silver brightness correction mask by using as the sensitive masking. element a panchromatic silver halide emulsion layer coated on a transparent support over which is coated a black silver filter layer, and over this a red sensitive emulsion layer. 'ffhe film is laminated base down to the multioolortransparency to be duplicated and exposed in, the. manner or theinyention with,forrexample; first green. light, then developed to silver; exposed with red light and developed cyanl The silver images are then bleached with a ferricyanidebromide bath. and a third exposure. to; red? light made through the originalfilm. Developmentis carried; out in a low energy developer-compounded as follows:

Sodium sulphite grams-.. 30 Paramethylamino phenolsulphate-unrdon. 1 Hydroquinone "M... do... 5 Borax do... 2 Potassium bromide do" 0.25 Water to liter-.. 1

From 50 to 100 mg. per liter of benzotriazol'e may be added to this developer to inhibit development of the rehalogenizedsilver; As a result, a silver mask is. developed in only the red sensitive emulsion layer since the developer does not develop rehalogenized silver. This leaves a cyan mask over the red colors, and in the top layer a silver'mask for correction for the impure absorptions of the dyes of the original and the reproduction processes. If a combined color and tone reproduction mask is desired in the top layer of this film it may be produced therein in the manner of Glasoe U. S. Patent 2,378,213 granted June 1-2, 1945 by exposing through the highlights 'of the original transparency with blue light, developing to a high gamma, bleaching with the ferricyanide-bromide bath then exposing; with red light and" developin in a low: gamma developer.

In another aspect ofthe invention, it is not uncommon to encounter in multi-l ayer subtractive- 1y colored films, a conditionin which the contrast of the yellow image is lower than the cyan and magenta images. This film or reproduction gives poor pictures, for example, a black object in the original is reproduced with a bluish cast because of the absence of yellow in the higher densities of the neutral scale. This cannot ordinarily be corrected by means of filters, such as yellow, in the reproduction process, because this causes veiling of the highlights with yellow before appreciable correction is obtained in the shadows. This deficiency is compensated for in the manner of the invention by exposing a panchromatic masking film with white light and developing a blackand-white image, the film is then flashed from the emulsion side of the maskin film and developed to a yellow positive mask in a color developer containing a yellow coupler. The silver is then removed by conventional means and the film fixed out. The result is a positive mask which when used in printing from the original raises the yellow gamma. The regular red light exposed silver brightness correction mask may also be used in printing with the yellow mask or the two masks may be produced from a single film carrying a panchromatic emulsion layer which is first exposed to red light through the original film, a silver image is then developed, a second exposure is made with blue light and a yellow dye image developed by means of coupler devel. "opment in the region of the exposure. The previous silver development prevents formation of yellow dye inareas having real transmission. By regulating the amount of blue light xposure, the desired amount. of yellow may be added to the bluecolors, including the blue areas: of the original which should: be printed: as black or gray.

The. invention having. thus: been: described. it, is to be. understood, that-the, disclosure herein is by way of example, and included in the invention are all modifications and equivalents following within the scope of the appended claims.

What we claim is:

1. The method of forming a brightness correction mask for a photographic color film having colored images composed of subtractive dye images some of said colored images of which appear of difierent brightness than other colored images and one of said dye images havin in a colored image area of said color film a scale of gamma different than the scale of said one dye image in a neutral exposure scale area of said color film, which comprises exposing through said color film a photographic element sensitive to the visible spectrum with light of wave length primarily absorbed by a dye image of said color film common to said colored images of different brightness, formin a silver image in the area of said 62-: posure, subjecting said photographic element to a second exposure through said color film and said silver image with light of wave length transmitted by said brighter images, and formin a colored image in the region of said second exposure of a color substantially the same as said first-mentioned dye image, and thereafter removing said silver image.

2. The method of forming a brightness correction mask for a photographic color film having colored images composed of subtractive dye images some of said colored images of which appear brighter than other colored images and one of said dye images having in a colored image area of said color film a scale of gamma greater than the gamma of said one dye image in a neutral exposure scale area of said color film, which comprises exposing through said color film a phcto graphic element sensitive to the visible spectrum with light of wave length primarily absorbed by a dye image of said color film common to said brighter colored images, forming a silver image in the area of said exposure, subjecting said photographic element to a second exposure through said color film and said silver image with light of wave length transmitted by said brighter images, and forming a colored image in the region of said second exposur of a color substantially the same as said first-mentioned dye image, and thereafter removing said silver image.

3. The method of forming a brightness correction mask for a photographic color film having colored images composed of subtractive dye images of which the red and magenta colored images appear brighter than other colored images and the cyan scale in a colored image area having a gamma greater than the cyan scale in the neutral exposure scale area of said color film, which comprises exposing through said color film a photographic element sensitive to the visible spectrum with green light, forming a silver image in the area of said exposure, subjecting said photo graphic element to a second exposure through said color film and said silver image with red light and forming a cyan image in the region of said second exposure, and thereafter removing said silver image.

4. The method of forming a brightness correction mask for a photographic color film having colored images composed of subtractive dye images of which the blue colored images appear brighter than other colored images and the yellow scale in a colored image area having a gamma greater than the yellow scale in the neutral exposure scale area of said color film, which comprises exposing through said color film a photographic element sensitive to the visible spectrum with red light, forming a silver image in the area of said exposure, subjecting said photographic element to a second exposure through said color film and said silver image with blue light and forming a yellow image in the region of said second exposure, and thereafter removing said silver image.

5. The method of forming a brightness correction mask for a photographic color film having colored images composed of subtractive dye images of which the green colored images appear brighter than other colored images and the magenta scale in a colored image area having a gamma greater than the magenta scale in the neutral exposure scale area of said color film, which comprises exposuring through said color film a photographic element sensitive to the visible spectrum with blue light, forming a silver image in the area of said exposure, subjecting said photographic element to a second exposure through said color film and said silver image with green light and forming a magenta image in the region of said second exposure, and thereafter removing said silver image.

' 6. The method of forming a brightness correction masl: for a photographic color film having colored images composed of subtractive dye images of which the red and magenta colored images appear brighter than other colored images, the cyan scale in a colored image area having a gamma greater than the cyan scale in the neutral exposure scale area of said color film, the magenta scale in the high exposure region of the red exposure scale having a lower density than in the region of no exposure of the red exposure scale, which comprises exposing through said color film a photographic element sensitive to the visible spectrum with green light, forming a silver image in the area of said exposure, subjecting said photographic element to a second exposure through said color film and said silver image with red light, and forming cyan and magenta images in the region of said second exposure, and thereafter removing said silver image.

7. The method of forming a brightness correction mask for a photographic color film having colored images composed of subtractive dye images of which the red and magenta colored images appear brighter than other colored images, the magenta scale in a colored image area having a gamma greater than the magenta scale in the neutral exposure scale area, the cyan density being less than the yellow density in a green image area, which comprises exposing through said color film with blue and red light, forming a silver image in the area of said exposure, subjecting said photographic element to a second exposure through said color film and said silver image with green light and forming a cyan image in the region of the second exposure, and thereafter removing said silver image.

PAUL K. GLASOE. DAVID DEAN.

REFERENCES CITED The followi ..g references are of record in the file of this patent:

UNITED STATES PATENTS Numb-er Name Date 2,186,053 Weaver Jan. 9, 1940 2,218,229 Carroll et al Oct. '15, 1940 2,348,735 Gaspar May 16, 1944 

